1. Field of the Invention
The present invention relates to an eyepiece which is used for example in telescopes and microscopes.
2. Related Background Art
Usually, such optical instrument as a telescope or microscope employes an eyepiece for further magnifying and observing a real image formed by an objective lens. Referring now to FIGS. 7 and 8, there is illustrated an example of the conventional eyepieces.
Shown in FIG. 7 is an eyepiece including, in the order from the eyepoint (E.P.) side, a first lens group G.sub.21 composed of a single positive lens component and a second lens group G.sub.22 of a positive refractive power composed of a cemented lens of a positive lens and a negative lens. The focal length f of this eyepiece is 10 mm and the apparent field of view is 51.degree.. The aberration diagram of this eyepiece is as shown in FIG. 8.
With such conventional eyepiece having a relatively large field angle, a relatively large distortion aberration appears as will be seen from FIG. 8. In order to provide a fully satisfactory aberration compensation even for the peripheral portion of the visual field in such eyepiece, there is a problem that the addition of a compensation optical system is required for this purpose and therefore the number of lenses used in the eyepiece system on the whole is inevitably increased. Particularly, the compensation of distortion aberration is difficult thus tending to result in a lens construction including 4 to 6 lenses.